Doctoral Theses and Dissertations

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Browsing Doctoral Theses and Dissertations by Author "Adesina, Adesoji"

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    Development of a System of MEA Solutions Activated by Novel Poyamines for Natural Gas Sweetening Mass Transfer in Absorber and Desorber Columns
    (Faculty of Graduate Studies and Research, University of Regina, 2020-03) Jaafari, Laila Ibrahim; Idem, Raphael; Torabi, Farshid; Tontiwachwuthikul, Paitoon; Supap, Teeradet; Raina-Fulton, Renata; Adesina, Adesoji
    This study focused on finding new and efficient activators to be blended with methyldiethanolamine (MDEA) for natural gas processing. Polyamines were highlighted in the open literature to have high CO2 loading as well as high absorption rate. As branched polyethyleneimine (PEI-B) (MW ≈ 800 with almost 16 amino groups) showed a superior performance in adsorption applications for capturing CO2, it was important to test its performance in absorption process. Tetraethylenepentamine (TEPA) is another polyamine (five amino groups) that was indicated in both adsorption and absorption as an excellent solvent; therefore, it was included in this study. PEI-B and TEPA were tested individually and as activators in MDEA blends. Furthermore, the performance of PEI-B and TEPA was evaluated against the performance of the standard activator of MDEA which is piperazine (PZ). Theses activators were screened using a simple absorption and desorption set up. In the screening experiments, the absorption and desorption temperatures were 40 and 100 ○C respectively. A dilute concentration for single polyamine (0.01 M) was applied at 100 mol% CO2 to investigate the maximum absorption rate at low viscosity and resistance in liquid and gas phases respectively. Also, higher amine concentrations of 0.1, 0.3, and 0.5 M were tested at 50 mol% CO2 to investigate their performance when both the solution viscosity and the gas resistance increased. Furthermore, in the screening step, these activators were tested in MDEA blends. The concentration of MDEA was kept constant at 3 M (30 wt%) while the concentration of the activators (PZ, TEPA, PEI-B) was varied at 0.1, 0.2 and 0.3 M. The performance of these activators individually and in MDEA blends was evaluated in terms of rich loading, lean loading, cyclic capacity, absorption rate and desorption rate. The results showed that PEI-B gave the highest performance individually and in MDEA blends followed by TEPA while PZ exhibited the lowest efficiency in all absorption and desorption parameters. Moreover, MDEA blends with PZ, TEPA and PEI-B were also investigated in a small pilot plant. Two blending ratios (0.1 and 0.3 M activator to 3 M MDEA) were selected to be tested in the pilot plant. Four CO2 contents of 20, 50, 70 % (the balance is N2) as well as 100 mol% were used in the gas feed. Again, PEI-B blends showed the highest absorption and desorption efficiencies followed by TEPA blends and then PZ blends. Also, the overall gas mass transfer coefficient (KGav) as well as the overall liquid mass transfer coefficient (KLav) were calculated to represent the mass transfer of CO2 in absorber and in desorber respectively. In both trends of KGav and KLav, PEI-B blends were recorded the best followed by TEPA blends and then PZ blends while non-activated MDEA gave the lowest mass transfer coefficients. Two models were applied for KLav and for KGav to predict their experimental values. The experimental values of KLav and KGav showed good fit with the models with acceptable average absolute deviations of 4.1 and 14.5 %, respectively.
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    Experimental Studies for Development of a Purification Process for Single and Mixed Amine Solvents
    (Faculty of Graduate Studies and Research, University of Regina, 2012-10) ElMoudir, Walid; Idem, Raphael; Tontiwachwuthikul, Paitoon; Murphy, R. Scott; deMontigny, David; Adesina, Adesoji
    Amine solvents used for the removal of CO2 from flue gas are subject to solvent degradation, which results from the reaction of impurities in the gas stream. This leads to the formation of degradation products, which could lead to many operational problems such as changes in the solvent absorption capacity and physical properties. Amine thermal (distillation) or non-thermal (ion-exchange or electrodialysis) reclamation are usually used to purify the solvents. In post-combustion CO2 1- The reclamation process might not effectively handle single or blended amine solvents. The solvent recovery could be low while its content in the waste stream could be high. The high consumption for water and energy cannot be justified. capture, thermal purification seems to be the only feasible method due to its ability to remove all types of degradation products. However, thermal reclamation has suffered from some challenges as follows: 2- Blended solvent could be difficult to purify due to the complicated nature of amine mixture with the degradation products. 3- The recovered solvent could be contaminated with light degradation products that have a closer boiling point to amine or are even lighter than amine. To develop an efficient reclamation process, laboratory investigation was carried out for monoethanolamine (MEA) and monoethanolamine/methyldiethanolamine (MEA/MDEA). MEA is considered a reference solvent while MEA/MDEA is a potential candidate solvent for CO2 capture. A number of degradation products were selected to create artificially-degraded solvents. The laboratory work was intended to address three issues: understanding the impact of degradation, testing batch thermal reclamation and activated carbon treatment of contamination in recovered solvent. The impact of degradation studies revealed that the degradation products have a noticeable impact on the solvent physical properties and absorption capacity. The measurement of density and refractive index showed proportional increases with degradation level. Moreover, the solvent absorption capacity diminished with increase of their concentrations. Process simulation of a CO2 In the thermal reclamation study, recovery of single and blended solvents was maximized to greater than 90-95% under deep vacuum. MEA was recovered in one step while MEA/MDEA was recovered in one or two steps. Optimum solvent recovery varied based on the degradation level and test conditions (temperature and pressure). capture plant with ProTreat shows that the plant suffers from the presence of heat stable salts (HSSs). Recovered single or blended solvents exhibited at least some level of contamination; however, MEA solvent had less contamination than MEA/MDEA which depended on the types of degradation products selected for each system and the reclamation conditions. Adsorption treatment with three activated carbon types to remove the contamination was successful in the case of MEA/MDEA (50-60% removal), while the contamination removal for the MEA solvent was unsatisfactory (<10%). Three industrial samples of degraded lean amine solvents were thermally purified and treated with adsorption. Almost all degradation products were eliminated in the two treatment steps, showing the new hybrid reclamation process (thermal at increased vacuum plus activated carbon) is a feasible method in treating industrial solvents.