Thesis (M.S.P.H.)--University of Michigan, 1941.

Thesis (M.S.P.H.)--University of Michigan, 1941.

Raw natural gas contains acid gases such as H2S and C02 which must be removed before the gas can be sold. The removal of these gases is called "sweetening" and the use of Diethanolamine (DEA) as a solvent has become widely accepted by industry. The process is simply based on the absorption and desorption of the acid gases in aqueous DEA. Side reactions can occur when DEA reacts with the C02 to produce degradation compounds. This degradation causes a loss in valuable DEA and an increase in plant operating costs. The reaction between DEA and C02 was studied experimentally, using a 600 ml stirred autoclave, to determine the effect of temperature, DEA concentration, and reaction pressure. Degraded DEA samples were analysed using gas chromatography. A fast, simple, and reliable technique was developed to analyse degraded DEA samples, which was ideally suited to plant use. Over 12 degradation compounds were detected in the degraded DEA solutions using gas chromatography and mass spectroscopy. Degradation mechanisms are proposed for the production of the various compounds. It was found that the degradation of DEA was very sensitive to temperature, DEA concentration, and C02 solubility of less than 0.2 g C02/g DEA. To study the effect of C02 solubility, which is a function of reaction pressure, simple solubility experiments were performed to cover the range of 100-200°C, 413.7-4137 kPa (60-600 psi) partial pressure of C02 and DEA concentration of 10, 20, and 30 wt % DEA. It was found that the reaction between DEA and C02 was extremely complex consisting of a mixture of equilibria, parallel, series, and ionic reactions. However, the overall degradation of DEA could be simply described by a pseudo first order reaction. The main degradation products were HEOD, THEED, and BHEP. It was concluded that C02 acted as a catalyst being neither consumed nor produced during the degradation of DEA to THEED and BHEP. HEOD was produced from DEA and C02, but was found to be unstable and could be converted back to DEA or react to form THEED and BHEP. The following simple kinetic model was developed to predict the degradation of DEA and the production of the major degradation compounds: [Figure 1] The model covered the ranges of DEA concentration 0-100 wt % DEA, 90-175°C, and C02 solubilities greater than 0.2 g C02/g DEA. Attempts were made to purify degraded DEA solutions. It has been claimed that activated carbon filters are useful in removing degradation compounds. However, tests with activated carbon proved it to be incapable of removing any of the major degradation compounds. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Diss. (sammanfattning) Umeå : Univ., 2007. / Härtill 5 uppsatser.

No description available.

Yes / This work evaluates the efficiency of the aqueous mixture of Methyl Diethanolamine (MDEA) and Diethanolamine (DEA) at various mass concentrations to remove CO2 and H2S from natural gas in an industrial sweetening unit in Fajr Jam Gas Refining Company located in the south of Iran and gives recommendations for modifying the process. The sweetening unit includes absorber and desorption towers, flash drum, lean and rich amine exchanger, kettle type reboiler and a reflux drum. The considered process is simulated by Promax simulator (version 3.2) taking into account operational constraints and sustainability of the environment. The validity of simulation has been evaluated by comparison between simulation results and the plant data. The main objective of this work is the modification of natural gas sweetening unit to achieve lower energy consumption. Thus, the effect of amine circulating rate and MDEA to DEA ratio on steam consumption in the regeneration tower, CO2 and H2S concentration in the treated gas, and the acid gas loadings have been investigated. Therefore, substitution of DEA solvent in the unit with the aqueous mixture of DEA and MDEA is proposed. In the examined cases, the mass concentration of MDEA and DEA lies between 15 and 45 wt% and 0–30 wt%, respectively, with the reference cases having MDEA 0 wt% and DEA 31.6 wt%. The results show that in the proposed cases of alternative mixtures including cases 1 (MDEA15 wt% and DEA 30 wt%), 2 (MDEA 20 wt% and DEA 25 wt%), and 3 (MDEA 25 wt% and DEA 20 wt%) the amount of reduction in amine circulation rate are between 11.1%v/v and 19.4%v/v compared to the original amine circulation rate. Likewise, steam consumption decreases between 24.4 %wt/wt and 27 %wt/wt. Influence of anti-foam injection for the different cases were also studied and it was found that anti-foam with the concentration of 5000 ppmv is more suitable for the optimum operation and is a more cost effective.

Over the past decade, membrane based gas separations have gained traction in industry as an attractive alternative to traditional thermally based separations due to their potential to offer lower operational and capital expenditures, greater ease of operation and lower environmental impact. As membrane research evolves, new state-of-the-art membrane materials as well as processes utilizing membranes will likely be developed. Therefore, their incorporation into existing thermally based units as a debottlenecking step or as a stand-alone separation unit is expected to become increasingly more common. Specifically for natural gas, utilization of smaller, more remote natural gas wells will require the use of less equipment intensive and more flexible separation technologies, which precludes the use of traditional, more capital and equipment intensive thermally based units. The use of membranes is, however, not without challenges. Perhaps the most important hurdle to overcome in membrane development for natural gas purification is the ability to maintain high efficiency in the presence of harsh feed components such as CO₂ and H₂S, both of which can swell and plasticize polymer membranes. Additionally, as this project demonstrates, achievement of similarly high selectivity for both CO₂ and H₂S is challenged by the different governing factors that control their transport through polymeric membranes. However, as others have suggested and shown, as well as what is demonstrated in this project, when CO₂ is the primary contaminant of interest, maintaining high CO₂/CH₄ efficiency appears to be more important in relation to product loss in the downstream. This work focuses on a class of fluorinated, glassy polyamide-imides which show high plasticization resistance without the need for covalent crosslinking. Membranes formed from various polyamide-imide materials show high mixed gas selectivities with adequate productivities when subjected to feed conditions that more closely resemble those that may be encountered in a real natural gas well. The results of this project highlight the polyamide-imide family as a promising platform for future membrane material development for materials aimed at aggressive natural gas purifications due to their ability to maintain high selectivities under aggressive feed conditions without the need for extensive stabilization methods.

No description available.

Mogrosides, the main active components in S. grosvenorii SWINGLE, are considered to be some 250 times sweeter than sucrose and to possess several medicinal attributes. Previous isolation processes used large quantities of toxic solvent that resulted in toxic residues of organic solvent in this high value food. Supercritical fluids fulfill the requirements of non-toxicity, recycle ability, and useful solvent characteristics. The work presented in this thesis is directed to the extraction of mogrosides from the powdered S. grosvenorii concentrate (SG) and the crude extract after resin treatment (MG) with sub critical water and supercritical CO2. / Because no source of mogroside V reference material is available commercially, the first objective of this research was to isolate mogroside V of sufficient purity that it could be crystallized. This objective was achieved by selecting suitable eluates from resin chromatography coupled with preparative thin layer chromatography (TLC). Crystalline white isolate was further characterized by 13C-NMR and by MS and determined to be mogroside V, which was suitable as a reference material for subsequent experiments. / The process variables for both sub critical water and supercritical carbon dioxide extraction were evaluated and optimized so that conclusions could be formulated regarding the relative merits of the two proposed extraction methods. The efficiency of extraction was determined spectrophotometrically based on the recovery of mogrosides from the starting material following the vanillin-HClO4 method. / When compared with Soxhlet solvent extraction, supercritical fluid extraction with either sub critical water or supercritical CO2 provided improved recoveries and consumed less organic solvent. In addition, the purity of the extracts differed greatly. For identical SG samples, sub critical water extraction was demonstrated to be more efficient (62.4% recovery) compared with 37.0% recovery by EtOH modified scCO2 extraction or 5.1% for Soxhlet extraction with hexane.

Orientadores: Maria Regina Wolf Maciel, Elenise Bannwart de Moraes Torres / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-11T12:26:54Z (GMT). No. of bitstreams: 1 Coelho_AdaodeMattos_M.pdf: 1833146 bytes, checksum: 1db62b866c35b28151164d26e378a710 (MD5) Previous issue date: 2007 / Resumo: Dois processos são muito utilizados no processamento do gás, o adoçamento e a desidratação. O adoçamento consiste na remoção dos gases ácidos, H2S e CO2, e a desidratação na remoção da água. Estes componentes ocasionam diversos problemas no manuseio e transporte do gás, dentre eles toxicidade, corrosão e a formação de hidratos. Isso leva à necessidade de remoção destas impurezas, normalmente, através de processos de absorção com líquido: soluções aquosas de aminas para o H2S e CO2 e trietilenoglicol para a água. Para o estudo destes processos, o uso de simuladores comerciais é bastante útil. Ao se utilizar os simuladores, diversos cuidados devem ser tomados, na escolha do modelo termodinâmico e do método de cálculo dos equipamentos. No caso do processo com aminas, absorção com reação química em meio eletrólito, a escolha do modelo é fundamental, além disso, o método de simulação afeta bastante os resultados. Este trabalho apresenta uma metodologia para analisar os diferentes modelos termodinâmicos e seleciona os melhores, depois de comparação com dados experimentais. Realizada a seleção, é introduzida uma nova metodologia para cálculo da eficiência, desenvolvida por Barros e Wolf, a qual é utilizada na simulação junto com o método de estágio de equilíbrio. Esta metodologia é uma alternativa ao método baseado na taxa de transferência de massa. As simulações sem o uso da eficiência resultam numa absorção praticamente completa do H2S e do CO2. Além disso, os valores destes componentes na corrente de gás tratado não são afetados com alterações nos parâmetros que, normalmente, afetam na absorção. Considerando a eficiência, foi possível identificar a influência destes parâmetros na absorção. A influência da eficiência é mais evidente no caso do processo de adoçamento do que na desidratação, devido ao fato de que o adoçamento é bastante influenciado pela transferência de massa. Foram realizadas análises de sensibilidade para otimizar o absorvedor e o regenerador, separadamente. Com estas condições otimizadas, foram apresentados ambos os processos com reciclo, enfocando a reutilização do solvente / Abstract: Two processes are widely used in the gas processing: sweetening and dehydration. Sweetening consists in removing acid gases, H2S and CO2, while dehydration is for water removing. The presence of these components causes several problems with the handling and transport of the gas like toxicity, corrosion and hydrate formation. So, it is clear the importance of removing these contaminants, which is normally made through absorption process with amines solutions, for H2S and CO2, and triethyleneglycol for water. For the study of these processes, the use of process commercial simulators is welcome. For the quality data acquisition with the simulator many cares must be taken, such as, the good choice of the thermodynamic model that represents the system and the suitable choice of the method for calculating of the equipments. In the amines process, where the absorption occurs with the chemical reaction in electrolyte environment, the model is fundamental; besides the simulation method affects the results. This work presents a methodology to analyze the different equilibrium models applicable for sweetening and dehydration processes and selects the best one after the comparison with experimental data. It was introduced a new methodology for the efficiency calculation developed by Barros and Wolf, which is used for the simulation with phase equilibrium based method. This methodology is an alternative for the use of rate based method. The simulation without the efficiency concept results in, practically, complete absorption of H2S e CO2. Further, the values of these components in the treated gas are not affected with modifications in the parameters that normally affect the absorption. Considering the efficiency, it was possible to identify the influence of these parameters in the absorption. The influence of the efficiency is more evident on the sweetening process than on the dehydration, due to the fact that the first process is highly influenced by mass transfer. Sensibility analyses were carried out in order to optimize the absorber and the regenerator, separately. With these optimized conditions, both processes were presented with recycle, focusing the reuse of the solvent / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química