Pressure swing absorption of carbon dioxide in propylene carbonate solutions

Zaprezentowano wyniki badań szybkości absorpcji i desorpcji CO2 z przesyconych roztworów węglanu propylenu. Badania prowadzono w okresowym reaktorze zbiornikowym z mieszadłem w zakresie temperatury (293,15÷323,15) K. Pomiar składał się z etapu absorpcji gazu, a następnie desorpcji wywołanej przez obniżenie ciśnienia gazu nad roztworem. W zależności od stopnia przesycenia roztworu zaobserwowano wystąpienie obszaru desorpcji dyfuzyjnej i nukleacyjnej. Otrzymane wyniki wskazują na wzrost szybkości desorpcji CO2 wraz ze wzrostem stopnia przesycenia roztworu, temperatury i szybkości obrotowej mieszadła.The rates of CO2 desorption from supersaturated propylene carbonate solutions were investigated at temperature range (293.15÷323.15) K using laboratory reaction calorimeter. Measurements were based on a batch isothermal absorption in the agitated vessel and subsequent desorption, which was initialized by the pressure release in the system. Based on the measured values of pressure change, the desorption rate was determined and compared with the absorption rate at the same driving force. The obtained results show that the CO2 desorption rate increases with increasing supersaturation, stirring speed and temperature. Two distinct mechanisms of desorption were observed depending on the supersaturation of the solution. For low supersaturations, the desorption process can be regarded as a reverse one to the absorption. The desorption rate under bubbling conditions was significantly greater than the absorption rate for the same driving force. The present finding would be helpful for design considerations of the regeneration step in several industrial processes for separating CO2 based on physical solvents. Although this study has provided an improved understanding of the desorption process, issues related to the quantitative description of the desorption kinetics under bubbling conditions need to be studied further

Pressure swing absorption of carbon dioxide in n-methyl-2-pyrrolidone solutions

The mass transfer rates during CO2 absorption and desorption from N-methyl-2-pyrrolidone solutions were measured at 293.15 K in a baffled agitated reactor with a flat gas-liquid interface. Based on the measured values of pressure changes, the desorption rate was determined and compared to the absorption rate at the same driving force. Two distinct mechanisms of desorption were observed. The transition from bubbling to the diffusive desorption is found to be a function of the supersaturation ratio, pressure and the stirring speed

Reaction kinetics of CO2 in aqueous methyldiethanolamine solutions using the stopped-flow technique

The kinetics of the reaction between CO2 and methyldiethanolamine in aqueous solutions have been studied using the stopped-flow technique at 288, 293, 298 and 303 K. The amine concentration ranged from 250 to 875 molźm-3. The overall reaction rate constant was found to increase with amine concentration and temperature. The acid base catalysis mechanism was applied to correlate the experimentally determined kinetic data. A good agreement between the second order rate constants for the CO2 reaction with MDEA computed from the stopped-flow data and the values reported in the literature was obtained

Mechanism of metal ion soprtion in chitosan hydrogel - calorimetric studies

Przedstawiono kalorymetryczne badania hydrożelu chitozanowego dotyczące mechanizmu sorpcji Cu(II), Ag(I) i Ca(II). Wyznaczono ciepła reakcji sorpcji tych jonów. Proces ten prowadzono dla maksymalnego stężenia danego jonu. Z pomiarów efektu cieplnego wynika, iż dla jonów Cu(II) i Ag(I) proces sorpcji ma charakter chemiczny (chemisorpcja). Efekt cieplny jest rzędu kilkudziesięciu kJ/mol. Natomiast jony Ca(II), które korzystnie wpływają na organizm ludzki, nie wykazują tego efektu.In the present research, studies were performed to determine the character of adsorption of Ca(II), Cu(II), Ag(I) ions in chitosan. The studies were carried out for chitosan hydrogel. The character of sorption was determined on the basis of calorimetric studies. The heat of reaction was measured during the sorption of individual ions. The process of adsorption was carried out for a maximum ion concentration. It follows from the measurement of the heat of sorption for Cu(II) and Ag(I) ions that the sorption process has a chemical character, which is shown by a measurable thermal effect of the order of dozens kJ/mol. It is interesting that Ca(II) ions which have an advantageous influence on living organisms, do not reveal this effect

A Selection of Amine Sorbents for CO2 Capture from Flue Gases

Amine absorption processes are widely used in the industry to purify refinery gases, process gases or natural gas. Recently, amine absorption has also been considered for CO2 removal from flue gases. It has a number of advantages, but there is one major disadvantage - high energy consumption. This can be reduced by using an appropriate sorbent. From a group of several dozen solutions, three amine sorbents were selected based on primary, tertiary and sterically hindered amines. The solutions were used to test CO2 absorption capacity, absorption kinetics and heat of CO2 absorption. Additional tests were performed on the actual absorber-desorber system to indicate the most appropriate sorbent for capturing CO2 from flue gases