The equilibrium partial pressures of monoethanolamine (MEA), piperazine (PZ), and water were measured in a stirred reactor with a recirculating vapor phase by FTIR analysis at 35 - 70 Celsius degrees. MEA and PZ volatility were measured in two separate pilot plant campaigns to capture CO₂ from flue gas under a range of absorber conditions. The laboratory data were regressed to determine NRTL binary interaction parameters that predicted the experimental points within 10 - 20%. It was proven that MEA volatility (0.45<MEA<0.55) is a viable concern in CO₂ capture processes from an economic, environmental, and overall health perspective. PZ, on the other hand, was not observed to be as volatile (0.06<PZ<0.08) as predicted by previous models and therefore volatility loss would not be a significant drawback for using it as a CO₂ capture solvent. Pilot plant results show an average MEA gas phase concentration at the absorber outlet to be approximately 45 ppm while the PZ concentrations averaged 6 ppm and 8 ppm at the absorber inlet and outlet, respectively.

No description available.

No description available.

Thesis (MEng)--Stellenbosch University, 2015. / AFRIKAANSE OPSOMMING: Raadpleeg die volteks vir opsomming, asseblief. / ENGLISH ABSTRACT: Please refer to full text for abstract

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: See item for full text / AFRIKAANSE OPSOMMING: Sien item vir volteks

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The discovery that the reaction of CO2 with primary amines in both aqueous and non-aqueous media provides a viable chemical method for determining the effective interfacial mass transfer area for separation column internals has lead to an increase in the interest of studying the reaction kinetics and determining the governing reaction rate expressions. For the absorption studies conducted on these systems, many authors assumed that power rate law reaction kinetics govern the reaction rate, which simplified the derivation of absorption correlations. This has already been proven to be an over simplifying assumption, since many authors suggest a non-elementary rate expression based on the pseudo-steady state hypothesis for the reactive zwitterion intermediate to be valid. An evaluation of the existing reaction rate expressions for the homogeneous liquid phase reaction of CO2 and mono-ethanolamine (MEA) in a 2-propanol solvent system was performed. The reaction rate profiles of CO2 and MEA at 25ºC, 30ºC and 35ºC, and relative initial concentrations of [MEA]i = [CO2]i, [MEA]i = 2.5[CO2]i, [MEA]i = 4[CO2]i were determined by means of an isothermal CSTR set-up. Scavenging of the unreacted MEA with benzoyl chloride provided the means to be able to stop the reaction in the product stream. This in turn allowed for the construction of concentration- and reaction rate profiles. The reaction rate data was modelled on various rate expressions by means of a MATLAB® non-linear estimation technique, employing the Levenberg-Marquard algorithm for minimizing the loss function. It was concluded that the rate expressions proposed in literature are insufficient and a rate expression derived fundamentally from first principals is proposed: [ ][ ] [ ] [ ][ ] [ ]2 MEA 1 2 2 -r = k CO RNH - k2 Z + k3 Z RNH2 - k4 S where ki are the reaction rate constants, Z is the zwitterion reactive intermediate and S the salt product of the overall reaction mechanism. In order to be able to determine the effective interfacial mass transfer area, the absorption rate per unit area or specific rate of absorption for the solute gas as a rate expression function of species concentration must firstly be determined. This is achieved by performing experimental absorption runs on a gas-liquid contactor of known surface area. This study incorporated the well known wetted wall experimental set-up. The aim was to construct and implement a wetted wall set-up and conduct absorption experiments for a gas side CO2 concentration range stretching from pure CO2 to diluted gas mixtures absorbing into solutions of varying MEA concentrations. Validation of the set-up was done by performing experiments at similar conditions to a previous study. The study then proceeded to determine the absolute and specific absorption rates at CO2 mass percentages of 100%, 78%, 55% and 30% into solutions of MEA concentrations of 0.25 and 0.3 mol/L. These runs were conducted at 25ºC and 30ºC. The wetted wall was designed to facilitate absorption studies at column heights of 60, 90 and 105mm. This allowed the investigation of the effect that surface area and column height has on the absolute rate of absorption as well as the CO2 and MEA concentrations in the liquid phase It was found that the specific absorption rate is independent of contact time, which is consistent with the rapid nature of the reaction. It was furthermore found that an increase in MEA concentration caused an increase in the absorption rate. The effect of temperature is linked with the solubility of CO2 in the solution. As the temperature increases, the solubility of CO2 decreases, but the absorption rate increases. The result is that it seems as if a change in temperature has no effect on the absorption rate, when in actual fact it does. An increase in the amount of CO2 absorbed is noticed for an increase in wetted wall surface area. This is expected and indicates that there is an increase in the amount of CO2 absorbed as the column length increases. Stopping the absorption reaction by means of MEA scavenging with benzoyl chloride at various column heights will allow for the construction of a concentration profile for both CO2 and MEA as a function of column height. These profiles will allow for the derivation of a non-elementary rate expression governing the specific absorption rate. This has been identified as ‘n area of great interest for future investigation. / AFRIKAANSE OPSOMMING: ‘n Groot navorsingsbelangstelling in die reaksiekinetika van CO2 en monoethanolamien (MEA) het ontstaan sedert die ontdekking dat hierdie reaktiewe sisteem ook ‘n goeie metode is vir die bepaling van die effektiewe massaoordragsoppervlakte van gestruktureerde pakkingsmateriaal. Die klem val op die bepaling van eerstens die mees geskikte en akkurate model om die reaksiekinetika te beskryf wat dan gebruik kan word om die absorbsiekinetika deeglik te karaktariseer. Sommige van die vorige navorsers het vereenvoudigende aannames gemaak rakende die reaksiekinetika ten einde die bepaling van geskikte absopsievergelykings te vergemaklik. Ander het gevind dat die nie-elementêre, pseudo-gestadigde toestand hipotese gebasseer op die reaktiewe zwitterioon tussenproduk van die reaksie ‘n meer verteenwoordigende kinetiese model is. Hierdie studie is eerstens gemik op die evaluasie van die bestaande reaksiekinetikavergelykings deur die homogene vloeistoffase reaksie van CO2 met mono-etanolamien (MEA) in die oplosmiddel, 2-propanol te ondersoek. Die studie is uitgevoer in ‘n isoterme CSTR sisteem by onderskeidelik 25ºC, 30ºC en 35ºC en MEA konsentrasies van [MEA]i = [CO2]i, [MEA]i = 2.5[CO2]i en [MEA]i = 4[CO2]i. Die voorgestelde reaksiekinetikavergelykings was gemodelleer met ‘n nie-lineêre datapassingstegniek verskaf deur die sagtewarepakket, MATLAB® wat die Levenberg- Marquard algoritme gebruik om die resfunksie te minimeer. Uit die teorie en datapassing word die volgende vergelyking voorgestel: [ ][ ] [ ] [ ][ ] [ ]2 MEA 1 2 2 -r = k CO RNH - k2 Z + k3 Z RNH2 - k4 S waar ki die reaksietempokonstante voorstel, Z die zwitterioontussenproduk en S die soutproduk. Die eerste stap in die bepaling van die effektiewe massaoordragsarea van gestruktureerde pakkingsmateriaal is om ‘n geskikte vergelyking of korrelasie vir die spesifieke absorpsie van die gas te bepaal. Dit word gedoen deur absoprsie eksperimente te doen op toerusting van bekende oppervlakarea. Hierdie studie het die reeds bekende ‘wetted wall’ opstelling gebruik. Die hoof doelwit van hierdie absorpsiestudie was om ‘n werkende opstelling te bou en absorpsie eksperimente vir CO2 konsentrasies wat strek van suiwer CO2 tot verdunde mengsels uit te voer. Die konsentrasie MEA is ook gevarieër. Die geskiktheid van die opstelling is eerstens getoets deur eksperimentele lopies uit te voer by soorgelyke toestande as ‘n vorige studie. Die doel van die studie is om die absolute en spesifieke absorpsietempos van CO2 by gasfase massapersentasies van 100%, 78%, 55% en 30% in MEA/2-propanol oplossings met MEA konsentrasies van 0.25 en 0.3 mol/L te bepaal. Die lopies is uigevoer by beide 25ºC en 30ºC. Die opstelling is ook ontwerp om absorpsie eksperimente by verskillende kolomhoogtes uit te voer. Hierdie hoogtes is 60, 90 en 105mm. Hierdie studie het tweedens gefokus op die effek wat absorpsiearea en kolomhoogte op die absorpsietempo van CO2 het. Die resultate van die studie toon dat die absorpsietempo onafhanklik is van kontaktyd. Dit stem saam met die vinnige reaksietempo. ‘n Toename in MEA konsentrasie het ‘n toename in spesifieke absorpsietempo tot gevolg, terwyl die effek van temperatuur gekoppel kan word aan die oplosbaarheid van CO2. Soos die temperatuur toeneem, neem die absolute absorpsietempo toe, maar die oplosbaarheid van CO2 neem af, dit het beide ‘n toenemende en afnemende effek op die spesifieke absorpsietempo. Die hoeveelheid CO2 geabsorbeer neem toe met ‘n toename in kolomhoogte. Die konsentrasie MEA in die uitlaatvloeistof toon ‘n skynbare eksponensiële afname met ‘n toename in kolomhoogte. ‘n Studie gemik om die konsentrasieprofiele van CO2 en MEA as ‘n funksie van kolomhoogte te bepaal, word voorgestel. Absorpsiemodelle en korrelasies kan dan afgelei word uit hierdie profiele, wat die berekening van die effektiewe massaoordragsarea akkuraat sal maak. Dit sal deel vorm van toekomstige navorsing.

This work includes wetted wall column experiments that measure the CO₂ equilibrium partial pressure and liquid film mass transfer coefficient (kg') in 7, 9, 11, and 13 m MEA and 2, 5, 8, and 12 m PZ solutions. A 7 m MEA/2 m PZ blend was also examined. Absorption and desorption experiments were performed at 40, 60, 80, and 100°C over a range of CO₂ loading. Diaphragm diffusion cell experiments were performed with CO₂ loaded MEA and PZ solutions to characterize diffusion behavior. All experimental results have been compared to available literature data and match well. MEA and PZ spreadsheet models were created to explain observed rate behavior using the wetted wall column rate data and available literature data. The resulting liquid film mass transfer coefficient expressions use termolecular (base catalysis) kinetics and activity-based rate expressions. The kg' expressions accurately represent rate behavior over the very wide range of experimental conditions. The models fully explain rate effects with changes in amine concentration, temperature, and CO₂ loading. These models allow for rate behavior to be predicted at any set of conditions as long as the parameters in the kg' expressions can be accurately estimated. An Aspen Plus® RateSep™ model for MEA was created to model CO₂ flux in the wetted wall column. The model accurately calculated CO₂ flux over the wide range of experimental conditions but included a systematic error with MEA concentration. The systematic error resulted from an inability to represent the activity coefficient of MEA properly. Due to this limitation, the RateSep™ model will be most accurate when finetuned to one specific amine concentration. This Aspen Plus® RateSep™ model allows for scale up to industrial conditions to examine absorber or stripper performance. / text

In Canada, coal-fired power plants are the largest anthropogenic point sources of atmospheric CO₂. The most promising near-term strategy for mitigating CO₂ emissions from these facilities is the post-combustion capture of CO₂ using MEA (monoethanolamine) with subsequent geologic sequestration. While MEA absorption of CO₂ from coal-derived flue gases on the scale proposed above is technologically feasible, MEA absorption is an energy intensive process and especially requires large quantities of low-pressure steam. It is the magnitude of the cost of providing this supplemental energy that is currently inhibiting the deployment of CO₂ capture with MEA absorption as means of combatting global warming. The steam cycle of a power plant ejects large quantities of low-quality heat to the surroundings. Traditionally, this waste has had no economic value. However, at different times and in different places, it has been recognized that the diversion of lower quality streams could be beneficial, for example, as an energy carrier for district heating systems. In a similar vein, using the waste heat from the power plant steam cycle to satisfy the heat requirements of a proposed CO₂ capture plant would reduce the required outlay for supplemental utilities; the economic barrier to MEA absorption could be removed. In this thesis, state-of-the-art process simulation tools are used to model coal combustion, steam cycle, and MEA absorption processes. These disparate models are then combined to create a model of a coal-fired power plant with integrated CO₂ capture. A sensitivity analysis on the integrated model is performed to ascertain the process variables which most strongly influence the CO₂ energy penalty. From the simulation results with this integrated model, it is clear that there is a substantial thermodynamic advantage to diverting low-pressure steam from the steam cycle for use in the CO₂ capture plant. During the course of the investigation, methodologies for using Aspen Plus?? to predict column pressure profiles and for converging the MEA absorption process flowsheet were developed and are herein presented.

Nas últimas décadas, tem havido um crescente interesse pelo desenvolvimento de novos sistemas propulsivos que permitam conciliar baixo custo, reduzido impacto ambiental, menor tempo de desenvolvimento e maior segurança de operação. Dentro deste contexto, este trabalho teve como objetivo o desenvolvimento de um combustível para motor foguete, com baixa toxicidade e elevada densidade de empuxo, à base de etanol e monoetanolamina catalisada com diferentes materiais catalíticos e hipergólico com o peróxido de hidrogênio (H2O2). Primeiramente, foi desenvolvido um sistema para concentração do H2O2. Paralelamente, foram estudados os fatores físicos e químicos que influenciam o tempo de indução do par hipergólico e elaborado um programa experimental para avaliar a velocidade de ignição dos diferentes combustíveis preparados a partir da dissolução de catalisadores em monoetanolamina. Dentre os materiais catalíticos testados o nitrato de cobre foi aquele que apresentou o melhor desempenho. A proporção dos constituintes do combustível, ideal, foi de 61,0% de monoetanolamina e 30,1% de etanol e 8,9% de Cu(NO3)2.3H2O em massa. Finalmente, os resultados analíticos e experimentais geraram informações para a fabricação e testes de um propulsor de 50 N de empuxo teórico, operando com este combustível e com H2O2 90% como oxidante. Este estudo mostrou que a adição de etanol ao sistema reduz, significativamente, o atraso de ignição e aumenta o impulso específico do sistema. O custo destes propelentes é bem inferior àqueles empregados tradicionalmente em propulsão e o desempenho bastante similar, não sendo, entretanto, agressivos ao meio ambiente. / In recent decades, interest in development of new propulsion systems has grown. The new systems reconcile low cost, reduced environmental impact, quick development, and safer operation. The objective of this study was to develop a rocket fuel that was not highly toxic and had high thrust density. The fuel is based on ethanol and monoethanolamine; Di_erent catalysts and hypergolic materials were used with hydrogen peroxide (H2O2). While an H2O2 concentration system system was developed, the physical and chemical factors that inuenced the induction time of hyperbolic pairs were studied and an experimental program was developed that would evaluate the ignition speed of di_erent catalysts that were dissolved in monoethanolamine. Copper nitrate was the best catalyst of those tested. The ideal ratio of fuel components was 61.0% monoethanolamine to 30.1% ethanol to 8.9% Cu(NO3) 2.3H2O by mass. Finally, the experimental and analytical results generated the information needed for manufacture and testing of the thruster. The thruster could theoretically generate 50 N of thrust using the ideal fuel and 90% H2O2 as an oxidant. This study showed that adding ethanol to the system signi_cantly reduced ignition delay and increased the system\'s speci_c thrust. This fuel costs much less that those that are normally used in rockets and the performance if very similar. In addition, it causes less damage to the environment.

In Canada, coal-fired power plants are the largest anthropogenic point sources of atmospheric CO₂. The most promising near-term strategy for mitigating CO₂ emissions from these facilities is the post-combustion capture of CO₂ using MEA (monoethanolamine) with subsequent geologic sequestration. While MEA absorption of CO₂ from coal-derived flue gases on the scale proposed above is technologically feasible, MEA absorption is an energy intensive process and especially requires large quantities of low-pressure steam. It is the magnitude of the cost of providing this supplemental energy that is currently inhibiting the deployment of CO₂ capture with MEA absorption as means of combatting global warming. The steam cycle of a power plant ejects large quantities of low-quality heat to the surroundings. Traditionally, this waste has had no economic value. However, at different times and in different places, it has been recognized that the diversion of lower quality streams could be beneficial, for example, as an energy carrier for district heating systems. In a similar vein, using the waste heat from the power plant steam cycle to satisfy the heat requirements of a proposed CO₂ capture plant would reduce the required outlay for supplemental utilities; the economic barrier to MEA absorption could be removed. In this thesis, state-of-the-art process simulation tools are used to model coal combustion, steam cycle, and MEA absorption processes. These disparate models are then combined to create a model of a coal-fired power plant with integrated CO₂ capture. A sensitivity analysis on the integrated model is performed to ascertain the process variables which most strongly influence the CO₂ energy penalty. From the simulation results with this integrated model, it is clear that there is a substantial thermodynamic advantage to diverting low-pressure steam from the steam cycle for use in the CO₂ capture plant. During the course of the investigation, methodologies for using Aspen Plus® to predict column pressure profiles and for converging the MEA absorption process flowsheet were developed and are herein presented.