Badie I. Morsi

Mass transfer characteristics in a large-scale slurry bubble column reactor with organic liquid mixtures

Abstract The mass transfer coefficients ( k L a ) and bubbles size distribution were measured in a large-scale (0.316-m inside diameter, 2.8-m high) slurry bubble column reactor (SBCR) for H 2 , CO, N 2 and CH 4 in two organic liquid mixtures (Isopar-M and a hexanes mixture) in the presence and absence of two solids (iron oxides catalyst and glass beads) in a wide range of pressure (0.17– 0.8 MPa ), superficial gas velocity (0.08– 0.2 m / s ), and solid concentration (0– 36 vol % ). The k L a values were found to intimately follow the behavior of the bubble size distribution under the operating conditions used, as they appeared to increase with pressure and gas velocity and dramatically decrease when operating with high solid concentrations. The effect of high solid concentrations in the reactor prevailed over the effect of pressure on the bubble size distribution by creating large gas bubbles with significantly small gas–liquid interfacial areas, leading to small k L a values. Thus, industrial SBCRs operating with high catalyst loading could likely operate in a mass transfer-controlled regime due to the expected low k L a values.

Critical and three phase behavior in the carbon dioxide/tridecane system

The PT behavior of the carbon dioxide/normal alkane series exhibits a distinct transition in the CO2/nC13H28 system. This particular diagram is characterized by two liquid—liquid—vapor (l-l-g) loci, a lower liquid-upper liquid (l-l) critical branch extending from high pressures to the upper critical end point (UCEP) and two liquid—vapor (l-g) critical branches which cross near the lower critical end point (LCEP). An experimental PTx diagram in the vicinity of the CO2 critical point, LCEP and K point reveals the emergene at the LCEP of a l-l region which increases in size with temperture while the upper liquid—vapor (L2-g) region diminishes, eventually disappearing at the K point. The l-l-g surface illustrates the compositional changes of each phase with temperture. Detailed Px diagrams at three temperatures between the LCEP and K point are presented and each exhibits two critical points, a l-l-g locus and curves of constant phase volume ratio which show discrete changes in both value and slope at the l-l-g locus. Graphical and numerical methods of determining the phase densities and compositions from three phase volumetric behavior are presented.

Interfacial area and liquid side mass transfer coefficient in trickle bed reactors operating with organic liquids

Abstract Interfacial area and liquid-side mass transfer coefficients measured in a 5cm diameter trickle-bed reactor operating with organic liquids are presented d p ≤ 2.4 mm and cylindrical catalyst of size 0.9 mm × 5 mm. A few data concern also 5.9 and 6.4 mm Raschig rings. Gas and liquid flowrates a Mass transfer parameters have been determined by the chemical technique using the carbamation of the reactants cyclohexylamine, monoethanolamine or die results obtained at low gas-liquid interaction with low liquid flowrate are reported for the ionic aqueous systems CO 2 -NaOH and O 2 -Na 2 SO 3 . The variation of the mass transfer data, the gas pressure drop and the liquid holdup with the gas and liquid flowrates show that there exists a strong connection between these parameters. This has led to correlate the with the liquid-solid friction factor within a + 30% accuracy.

Prediction of the gas–liquid volumetric mass transfer coefficients in surface-aeration and gas-inducing reactors using neural networks

Abstract Almost all available literature correlations to predict the volumetric gas–liquid mass transfer coefficient, k L a in agitated reactors are systems- or operating conditions-dependent. In this study, two back-propagation neural networks (BPNNs), one dimensional and one dimensionless were developed to correlate k L a for numerous gas–liquid systems in both surface-aeration reactors (SAR) and gas-inducing reactors (GIR) operating under wide ranges of industrial conditions. A total of 4435 experimental data points obtained from more than 10 publications for 50 gas–liquid systems were used to train, validate the dimensional and dimensionless BPNNs, which were able to correlate all k L a values with R 2 of 90.5 and 88.6%, respectively. The dimensional BPNN was used to predict the effect of various operating parameters on k L a in a number of important industrial processes. The predictions showed that increasing liquid viscosity decreased k L a values in the SAR, while k L a values in the GIR increased and then decreased with increasing liquid viscosity, following the gas holdup behavior. Increasing liquid density decreased k L a in both reactor types. Increasing liquid surface tension increased k L a values in the SAR, whereas in the GIR, k L a decreased due to the increase of bubble size. Increasing gas diffusivity or gas partial pressure or mixing speed, increased k L a in both reactor types. k L a values in the GIR were always higher than those in the SAR and increasing D Imp. / D T and H F / H L increased k L a in both reactor types.

Effect of water on the solubility and mass transfer coefficients of CO and H2 in a Fischer-Tropsch liquid

Abstract The effects of water on the solubilities (C*) and mass transfer coefficients (kLa) for CO and H2, in a medium fraction (C11 – C22 of Fischer-Tropsch (FT) liquid were examined at elevated temperatures (423 – 498 K) and pressures (1 – 4 MPa, and at different stirring speeds. A new procedure, which utilizes only pressure-temperature data for FT liquid-water mixtures to estimate the equilibrium solubility of water in FT fraction is presented. The equilibrium solubility values of water in FT liquid increased with temperature and were higher than those reported in the literature for higher paraffins. The solubilities of CO and H2 in FT liquid saturated with water increased with both pressure and temperature, and Henrys law behavior was adequate to express the experimental values. The C* values for H2 appeared to be more sensitive to the presence of water than those for CO. kLa values for H2 at 700, 1000 and 1200 rpm decreased with the presence of water in FT liquid. For CO, however, kLa values obtained at 1000 and 1200 rpm were higher in FT liquid saturated with water than those obtained in FT liquid containing no water. kLa values for both CO and H2 increased considerably with the specific power input and slightly with pressure and temperature.

A Thermodynamic Correlation for the Minimum Miscibility Pressure in CO2 Flooding of Petroleum Reservoirs

A graphic equation-of-state (EOS)-generated correlation for the minimum miscibility pressure (MMP) of CO/sub 2//crude-oil displacements is presented, along with a brief review of 17 other MMP correlations. The MMP is estimated as the cricondenbar or first-contact miscibility pressure of the pure or impure CO/sub 2//crude-oil system in which the C/sub 5+/ oil fraction is modeled as a single normal alkane of equivalent molecular weight. The correlation accounts for all the experimentally observed trends in MMP in a consistent manner and is independent of any CO/sub 2//crude-oil data base. A correction is introduced, however, to prevent a predicted increase in the MMP with decreasing temperature at low temperatures for high-molecular-weight oils. The average predicted-MMP/experimental-MMP ratio for 157 CO/sub 2//crude-oil MMP values is 1.09, with a standard deviation of 0.19. Unlike other correlations, specifically those relating MMP with CO/sub 2/ density, a decrease in MMP with temperature at elevated temperatures (>120/sup 0/C (>248/sup 0/F)) is predicted.

Gas-liquid mass transfer in cyclohexane oxidation process using gas-inducing and surface-aeration agitated reactors

Abstract The equilibrium solubilities, C ∗ , and volumetric liquid-side mass transfer coefficients (kLa) for gaseous nitrogen and oxygen in liquid cyclohexane were obtained in wide ranges of pressures (1–40 bar), temperatures (380–480 K) and mixing speeds (13.3–20 Hz) in gas-inducing (GIR) and surface-aeration (SAR) agitated reactors. The C ∗ values were calculated using a modified Peng-Robinson equation of state and the transient physical gas absorption technique was employed to obtain the mass transfer coefficients. The C ∗ values for both N2 and O2 were found to increase with the solute gas equilibrium partial pressure and temperature. Under the same operating conditions, O2 appeared to be more soluble in cyclohexane than N2. The kLa values for the two gases were found to increase strongly with mixing speed and slightly increase with pressure in both reactor types. kLa values for both gases appeared to slightly increase with temperature in the SAR while an opposite trend was observed in the GIR. kLa values for both gases in the GIR were higher than those in the SAR at higher mixing speeds (16.6 and 20.0 Hz). It appeared that kLa values in the SAR were controlled by the mass transfer coefficient, kL, whereas those in the GIR were controlled by the gas-liquid interfacial area. a. The effect of gas nature on kLa values in both reactors was insignificant. Two empirical correlations to predict kLa and gas holdup values for N2 and O2 in liquid cyclohexane in both reactor types with ±30% accuracy were developed.

Hydrodynamics and gas-liquid-solid interfacial parameters of co-current downward two-phase flow in trickle-bed reactors

Abstract Design of trickle-fixed bed reactors requires knowledge of the hydrodynamics of two-phase co-current downward flow through fixed porous catalytic media and interfacial parameters. Unfortunately, most of the published papers deal exclusively with the hydrodynamics of an air-water system and the determination of gas-liquid-solid interfacial parameters in highly ionic solutions. In this paper, we present some experimental results on the hydrodynamics, pressure drop, liquid holdup, different flow patterns, gas-liquid interfacial areas and liquid-side mass transfer coefficients for organic non-viscous and viscous liquids and liquid-solid mass transfer coefficients with different packings: glass beads (dp = 1.16 × 10−3 m and 4 × 10−3 m), spherical catalyst (dp = 2.4 × 10−3 m) and glass Raschig rings (dp = 6.48 × 10−3 m). Comparison between our values and correlations in the literature will be discussed.

Gas-liquid mass transfer in a slurry reactor operating under olefinic polymerization process conditions

Abstract The equilibrium solubilities, C ∗ , and the volumetric liquid-side mass transfer coefficients, kLa, of propylene, ethylene and hydrogen in liquid n-hexane containing up to 30 wt% solid polypropylene powder were obtained in a 4−1 agitated batch reactor operated in surface-aeration mode. The data were collected under pressures between 2 and 55 bar, temperatures from 313 to 353 K, mixing speeds from 13.3 to 20.0 Hz and solid concentrations between 0 and 30 wt%. The gas solubilities were calculated using a modified Peng-Robinson equation of state (PR-EOS) and the mass transfer coefficients were determined using the transient physical gas absorption technique. The solubilities of hydrogen, ethylene and propylene in n-hexane were found to obey Henrys law and the values were not affected by the presence of solids. The gas with the closest solubility parameter to that of liquid n-hexane appeared to have the highest solubility. As expected, the mass transfer coefficients of the three gases in liquid n-hexane with and without solids increased with increasing mixing speed. The kLa values of hydrogen in n-hexane and slurries were found to slightly increase whereas those of ethylene and propylene slightly decrease with increasing the mean partial pressure of the gas component. The temperature appeared to have no effect on kLa values of hydrogen in n-hexane with and without solids while those of ethylene and propylene were slightly increased with temperature. The kLa values for the three gases increased at low solid concentration (10 wt%) and decreased at high solid concentration (30 wt%). A dramatic decrease of kLa values for ethylene and propylene in liquid n-hexane was observed at particular operating conditions (T = 353 K, N = 13.3 Hz, Ws = 30 wt% and P1,m≥5 bar). This behavior was attributed to the high slurry viscosity prevailed under these particular conditions. The kLa values of the three gases used in n-hexane were correlated with operating variables using empirical correlations.

Determination of sulfur forms on coal surfaces by X-ray photoelectron spectroscopy

Abstract X-ray photoelectron spectroscopy (XPS or ESCA) was used to monitor changes in the amount of organic and pyritic sulfur, and inorganic sulfur present on coal surfaces following hydrochloric and nitric acid treatments. The results show that after treatment with HCl the oxidized sulfur was totally removed from the surface. Subsequent leaching with HNO 3 decreased the atomic abundance of sulfide forms on the coal surface.