Interfacial Area and Gas Holdup in an Agitated Gas-Liquid Reactor under Pressure

The solubility, volumetric mass transfer coefficient, gas−liquid interfacial area, mass transfer coefficient, gas holdup, and bubble Sauter mean diameter for O2 and N2 in liquid cyclohexane were obtained in 4-L gas-inducing and surface-aerated agitated reactors. The modified Peng−Robinson equation of state and the transient gas absorption and photographic techniques were employed. The experiments were statistically designed and the results were statistically correlated with a 95% confidence level. The solubilities for O2 and N2 showed an increase with pressure and temperature, and Henry's law adequately modeled the values. All mass transfer parameters obtained were found to be higher in the gas-inducing than those in the surface-aerated reactor. Mixing speed and liquid height significantly affected the volumetric mass transfer coefficients and gas holdup in both reactors. The pressure and temperature slightly affected the volumetric mass transfer coefficients whereas the bubbles Sauter mean diameter for both gases remained constant at about 0.76 mm.

Section: Volumetric Mass Transfer Coefficient K L Asupporting

confidence: 92%

Section: Volumetric Mass Transfer Coefficient K L Asupporting

confidence: 90%

Mass Transfer Parameters of O₂ and N₂ in Cyclohexane under Elevated Pressures and Temperatures: A Statistical Approach

Tekie

Morsi

1997

“…The interfacial area can be deduced from the overall rate of absorption. This system has been reported elsewhere; see Stegeman et al (1995) for a more thorough description.…”

Section: Methodsmentioning

confidence: 99%

Interfacial Area and Gas Holdup in a Bubble Column Reactor at Elevated Pressures

Stegeman

Knop

Wijnands

et al. 1996

The influence of pressure, liquid viscosity, and gas velocity on the gas holdup and specific gas−liquid interfacial area in a bubble column reactor has been studied. The 18.7 L reactor had an inner diameter of 15.6 cm with a dispersion height set equal to 3 times the diameter and was operated at pressures between 0.1 and 6.6 MPa. By means of the chemically enhanced absorption of CO2 in diethanolamine, the gas−liquid interfacial area in the reactor has been determined. The viscosity has been changed in the range from 1 to 9.4 mPa·s by adding ethylene glycol to the mixture. It is determined that pressure has a small effect on the gas holdup in pure water, whereas it shows a pronounced effect for the more viscous liquids. This can be attributed to the influence of the increased pressure on the flow regime transition. For the most viscous liquid all interfacial area data were obtained in the fully heterogeneous regime. Here the interfacial area increased with increasing pressure and was moderately affected by the gas velocity. For the less viscous liquids both pressure and gas velocity affect the interfacial area; this influence depends on the flow regime. Therefore, the state of the flow regime has an important impact on the mode in which the operating parameters affect the interfacial area.

“…In the process of absorption, the variation of the total gas flow rate along the height of the column is little as the volume percentage of the inert gas in gas stream is above 92%. Therefore, it is reasonable to assume that the gas phase velocity u G is unchanged and the liquid phase CO 2 concentration or the CO 2 partial pressure equilibrium with the liquid y * is zero. ,− The volumetric mass transfer coefficient ( K G a e ) is considered to be constant. Under these conditions, integration of eq over the packed height ( Z ) yields the following expression for the K G a e K normalG a normale = u normalG Z R T .25em ln ( y CO 2 , in y CO 2 , out ) …”

Section: Determination Of Overall Mass Trasnfer Coefficientmentioning

confidence: 99%

“…The source term S C in eqs and , representing the net mass sink of the gas due to the CO 2 absorbed by the aqueous ammonia solution, are given by the following equation: S normalC = K normalG a normale M CO 2 ( P CO 2 * − P CO 2 ) / 3600 where M CO 2 is the molecular weight of CO 2 , P CO 2 is the partial pressure of CO 2 in main body of gas, P CO 2 * is the partial pressure of CO 2 in equilibrium with the aqueous ammonia solution, and as mentioned above, P CO 2 * is approximately zero, ,− and the overall mass transfer coefficient K G a e is determined by the proposed correlation in the section .…”

Section: Simulationmentioning

confidence: 99%

Mass Transfer Coefficients for CO₂ Absorption into Aqueous Ammonia Using Structured Packing

Zhao

Liu

et al. 2014

In this study, the gas phase volumetric overall mass transfer coefficients (K G a e ) for CO 2 absorption into aqueous ammonia solutions were measured to explore the mass transfer performance of a column packed with structured packing. The K G a e values were evaluated over ranges of main operating variables, that are, 1400−2300 m 3 ·m −2 ·h −1 gas flow rate, 20−39 m 3 · m −2 ·h −1 liquid flow rate, up to 8 kPa partial pressure of CO 2 , and 0.27−0.72 kmol·m −3 ammonia concentration. The results show that higher liquid loading and concentration of aqueous ammonia are beneficial to enhance the K G a e values. On the contrary, K G a e value decreases as the CO 2 partial pressure increases. The results also show that gas loading has little influence on K G a e . To allow the mass transfer data to be readily utilized, an empirical K G a e correlation for this system was developed. Finally, Simulations were made for the absorption of CO 2 into aqueous ammonia solutions by using the currently developed computational mass transfer model along with the proposed correlation for K G a e . The simulation results on the gas phase CO 2 concentration are found to be in satisfactory agreement with the experimental measurements.