CO2 capture by pyrrolidine: Reaction mechanism and mass transfer

A new carbon dioxide capture process by means of gas–liquid absorption using pyrrolidine aqueous solutions in a bubble column reactor obtaining suitable results in comparison with other commonly used amines is analyzed. The influence of several operation variables such as amine concentration and gas flow rate has been studied. Carbon dioxide mass‐transfer rate data have shown a different behavior than other amine‐based systems because a constant value in absorption rate was observed in the middle of batch experiments. ¹³C and ¹H NMR spectroscopy studies were performed to analyze the species present during the experiments. These data and the carbon dioxide loading allowed to explain the reaction mechanism existed between these reagents. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1098–1106, 2014     

Influence of Chitosan and Chitosan Derivatives on Hydrodynamics and Mass Transfer in a Bubble Contactor

The behavior of chitosan and two kinds of chitosan derivatives in carbon dioxide absorption in a bubble column contactor is analyzed. The effects of absorption type (physical or chemical), polymer type, concentration, and liquid‐phase physical properties on hydrodynamics (bubble size, gas holdup, and specific interfacial area) and mass transfer (absorption rate and mass transfer coefficient) are evaluated.     

Interfacial area and mass transfer in gas-liquid cocurrent upflow and countercurrent flow in reciprocating plate column

The volumetric mass transfer coefficient and the interfacial area were measured for carbon dioxide absorption into water using a reciprocating plate column of plate geometry different from a Karr column. The specific interfacial area was governed by a change in bubble size at low agitation rates and by a variation in gas holdup at high agitation rates. The liquid phase mass transfer coefficient was strongly influenced by the agitation rate, the phase velocities and the plate geometry.     

Effect of Carbon Dioxide Chemical Absorption on Bubble Diameter and Interfacial Area

The influence of a gas‐liquid chemical reaction on the interfacial area produced in a contactor is analyzed. Two different amines were used to capture carbon dioxide by chemical absorption. The effects of the operation time, the amine used, the concentration interval, and the gas flow rate on typical hydrodynamic parameters used in bubble columns such as the gas holdup and the Sauter mean diameter were investigated. These parameters were used to determine the interfacial area value. Significant influences on the gas‐liquid interfacial area were detected, mainly caused by the reaction rate intensity, the physicochemical properties of the liquid phase, and the gas flow rate fed to the contactor.     

Gas absorption in the plunging liquid jet reactor

A pseudo first-order gas absorption survey has been made of the contacting system formed when a coherent liquid jet plunges through an ambient reactive gaseous atmosphere into a bath of jet liquid. Using the hypochlorite ion catalysed reaction between pure carbon dioxide and a carbonate ion-bicarbonate ion buffer solution, the reactor has been found to be analogous to a gas sparged stirred tank contactor with the plunging jet acting as both the reactor agitator and gas bubble generator. Resolution of the gas—liquid interfacial area and rate of surface renewal absorption parameters was thus made possible. Specific interfacial areas in the range 20–110 m^?1 and rates of surface renewal in the range 40–160 sec^?1 for the subsurface reactor have been related to the plunging jet surface roughness and velocity or the entrainment rate of the plunging jet.     

Influence of Pressure on the Hydrodynamics and Mass Transfer Parameters of an Agitated Bubble Reactor

The present study deals with the pressure effects on the hydrodynamic flow and mass transfer within an agitated bubble reactor operated at pressures between 10⁵ and 100 × 10⁵ Pa. In order to clarify the flow behavior within the reactor, liquid phase residence time distributions (RTD) for different operating pressures and gas velocities ranging between 0.005 m/s and 0.03 m/s are determined experimentally by the tracer method for which a KCl solution is used as a tracer. The result of the analysis of the liquid‐phase RTD curves justifies the tank‐in‐series model flow for the operating pressure range. Good agreement is obtained between theoretical and experimental results assuming the reactor is operating as perfectly mixed. Two parameters characterizing the mass transfer are identified and investigated in respect to pressure: the gas‐liquid interfacial area and volumetric liquid‐side mass transfer coefficient. The chemical absorption method is used. For a given gas mass flow rate, the interfacial area as well as the volumetric liquid mass transfer coefficient decrease with increasing operating pressure. However, for a given pressure, a and k_La increase with increasing gas mass flow rates. The mass transfer coefficient k_L is independent of pressure.     

Chemical absorption in a bubble column loading concentrated slurry

Carbon dioxide was absorbed into aqueous slurries of magnesium hydroxide or calcium hydroxide particles in a bubble column at 308 K and 0.1013 MPa. The volumetric mass transfer coefficient and the effective gas-liquid interfacial area were obtained separately by these absorption experiments. It was found that the liquid-side physical mass transfer coefficient as well as the effective gas-liquid interfacial area decrease with increasing the slurry concentration and that there is an optimal point of fine reactant particle concentration where the chemical absorption rate has its maximum value. The process of gas absorption into slurry in a bubble column was formulated by a film-theory model incorporating a finite dissolution rate of solid particles. The observed absorption rates of carbon dioxide into calcium hydroxide slurries in the bubble column were successfully predicted by the proposed model.     

Gas-liquid mass transfer in trickle-bed reactors: Gas-side mass transfer

New data of gas-liquid mass transfer for cocurrent downflow through packed beds of non-porous particles are presented. Mass transfer parameters for air/carbon dioxide/water and air/carbon dioxide/sodium hydroxide systems were evaluated by least squares fit of the calculated CO₂ concentration profiles in the gas phase to the experimental values. The dependence of k_Ga on gas and liquid flow rates is caused by the dependence of gas-liquid interfacial area, not by the gas-side mass transfer coefficient k_G. In the case of the absorption of dilute carbon dioxide the gas-side resistance is considerably smaller than the liquid-side resistance. In the pulse flow regime, gas-liquid interfacial area calculated from k_La and k_L values obtained by physical, respectively, chemical absorption are lower than the gas-liquid interfacial area evaluated from the measurements under reaction conditions.     

Interfacial area and mass transfer in carbon dioxide absorption in TEA aqueous solutions in a bubble column reactor

The hydrodynamic behaviour and mass transfer of carbon dioxide removal process by aqueous solutions of triethanolamine (TEA) are analysed. The experiments were made in a bubble column reactor (BCR) as gas–liquid contactor. The interfacial area and mass transfer coefficient were calculated by using a photographic method based on the bubble diameter determination. The influence of operation conditions, liquid phase nature and chemical reaction on the mass transfer coefficient and gas–liquid interfacial area has been also analysed.     

Investigation of the effect of magnetic field on mass transfer parameters of CO2 absorption using Fe3O4‐water nanofluid

In this study, the enhancement of physical absorption of carbon dioxide by Fe₃O₄‐water nanofluid under the influence of AC and DC magnetic fields was investigated. Furthermore, a gas‐liquid mass transfer model for single bubble systems was applied to predict mass transfer parameters. The coated Fe₃O₄ nanoparticles were prepared using co‐percipitation method. The results from characterization indicated that the nanoparticles surfaces were covered with hydroxyl groups and nanoparticles diameter were 10–13 nm. The findings showed that the mass transfer rate and solubility of carbon dioxide in magnetic nanofluid increased with an increase in the magnetic field strength. Results indicated that the enhancement of carbon dioxide solubility and average molar flux gas into liquid phase, particularly in the case of AC magnetic field. Moreover, results demonstrated that mass diffusivity of CO₂ in nanofluid and renewal surface factor increased when the intensity of the field increased and consequently diffusion layer thickness decreased. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2176–2186, 2017     

Mass transfer with chemical reaction in liquid foam reactors

Mass transfer studies were conducted in a stable liquid foam reactor under various operating conditions to evaluate gas holdup, effective interfacial area, liquid-phase mass transfer coefficient and a modified interfacial mass transfer coefficient to include the surface-active agents employed. Gas holdup and effective interfacial area were evaluated experimentally. The interfacial mass transfer coefficient was evaluated semitheoretically, by considering the interfacial region as a separate phase and using the experimental data developed for mass transfer accompanied by a fast first-order chemical reaction. The liquid-phase mass transfer coefficient was also evaluated semitheoretically, using Danckwert's theory for the liquid phase and the experimental data on mass transfer accompanied by a slow pseudofirst-order chemical reaction. An experimental unit was set up to provide a stable flowing foam column, simulating the foam reactor. Mass transfer rates were studied for superfacial gas velocities in the range from 1.5 × 10⁻² m/s to 5 × 10⁻² m/s, giving gas residence times in the range from 20 to 55 seconds. A cationic and nonionic surface-active agent and three different wire mesh sizes, giving bubble size distributions in the range from 2.2 to 5.4 mm Sauter mean diameters, were employed. It is observed that gas holdup is insensitive to the type of surface-active agent; it is however, dependent on wire mesh size and gas velocity. The bubble diameter and, hence, the interfacial area are found to be insensitive to gas velocity in the range studied; they are, however, strong functions of wire mesh size. The liquid-phase mass transfer coefficient increases with increase in gas velocity. The surface-active agent introduces additional resistance to mass transfer in both reaction cases, this being the controlling one in the case of the fast reaction. A comparison with conventional packed bed contactors indicates the mass transfer rates to be about 8 times lower for the foam reactor, for the fast reaction case; for slow reactions, the foam reactor has mass transfer rates approximately 2-4 times higher than those for conventional packed bed contactors.     

Gas–liquid interfacial area and mass transfer coefficient in a co‐current down flow contacting column

The gas–liquid interfacial area and mass transfer coefficient for absorption of oxygen from air into water, aqueous glycerol solutions up to 1.5% (w/w) and fermentation medium containing glucose up to a 3% concentration were determined in a co‐current down flow contacting column (CDCC; 0.05 m i.d. and 0.8 m length). Experimental studies were conducted using various nozzle diameters at different gas and re‐circulation liquid rates. Specific interfacial area (a) is determined from the fractional gas hold‐up (ε_G) and the average bubble diameter (d_b). Once the interfacial area is determined, the volumetric mass transfer coefficient (k_La) is then used to evaluate the film mass transfer coefficient in the CDCC. The effects of operating conditions and liquid properties on the specific interfacial area were investigated. The values of interfacial area in air–aqueous glycerol solutions and fermentation media were found to be lower than those in the air–water system. As far as experimental conditions were concerned, the values of interfacial area obtained from this study were found to be considerably higher than those of the literature values of conventional bubble columns. The penetration theory is used to interpret the film mass transfer coefficient and results match the experimental k_L data reasonably well. Copyright © 2006 Society of Chemical Industry     

Mass transfer with chemical reaction during gas absorption on a sieve plate

On the basis of measurements of the rate of absorption of carbon dioxide into potassium carbonate—potassium bicarbonate buffer solutions, containing sodium hypochlorite and potassium chloride, and into sodium hydroxide solutions it has been proved that the Danckwerts' pseudo-first order reaction method may be successfully used for the determination of interfacial area and mass transfer coefficients on sieve plates.The values of interfacial area and mass transfer coefficient have been measured by this method for sieve plates of various geometry, at different gas velocities and clear liquid heads. It was found that the interfacial area per unit volume of the froth is almost independent of these parameters.A method of computation of the plate efficiency for absorption with reaction process has been suggested and tested experimentally.The results of investigations of the kinetics of the chemical reactions involved are also given.     

Effective interfacial area and liquid and gas side mass transfer coefficients in a packed column

The theory of gas absorption accompanied by fast pseudo-mth order reaction was used to obtain values of effective interfacial area in a packed column, irrigated with aqueous solutions and provided with 1 in. ceramic Raschig rings, 1 in. P.V.C. Raschig rings, 1 in. ceramic Intalox saddles, 1 in. polypropylene Intalox saddles, 1 in. stainless steel Pall rings and 1 in. polypropylene Pall rings. The values of liquid side mass transfer coefficient were obtained by physical absorption of carbon dioxide in water. In addition, the values of gas side mass transfer coefficient for a range of gas and liquid flow rates were obtained.     

Oxygen mass transfer coefficient in bubble column slurry reactor with ultrafine suspended particles and neural network prediction

The gas–liquid volumetric mass transfer coefficient was determined by the dynamic oxygen absorption technique using a polarographic dissolved oxygen probe and the gas–liquid interfacial area was measured using dual‐tip conductivity probes in a bubble column slurry reactor at ambient temperature and normal pressure. The solid particles used were ultrafine hollow glass microspheres with a mean diameter of 8.624 µm. The effects of various axial locations (height–diameter ratio = 1–12), superficial gas velocity (u_G = 0.011–0.085 m/s) and solid concentration (ε_S = 0–30 wt.%) on the gas–liquid volumetric mass transfer coefficient k_La_L and liquid‐side mass transfer coefficient k_L were discussed in detail in the range of operating variables investigated. Empirical correlations by dimensional analysis were obtained and feed‐forward back propagation neural network models were employed to predict the gas–liquid volumetric mass transfer coefficient and liquid‐side mass transfer coefficient for an air–water–hollow glass microspheres system in a commercial‐scale bubble column slurry reactor. © 2012 Canadian Society for Chemical Engineering     

Absorption in packed bubble columns

The mass transfer characteristics of packed bubble columns were studied by employing various packings of different sizes and shapes in 10–38·5 cm i.d. columns. The theory of absorption accompanied by pseudo-mth order reaction was used to obtain the values of effective interfacial area. The values of liquid side mass transfer coefficient were obtained by using the theory of absorption accompanied by slow chemical reaction. The superficial gas velocity was varied from 5 to 25 cm/sec. The packed bubble columns showed a considerable improvement in the performance over empty bubble columns. A criterion for the scale-up of these columns has been suggested.     

Counter-current absorption using wire gauze packings

The dynamic liquid hold-up, ?_LD, effective interfacial area, a, and the liquid side mass transfer coefficient k_La were determined for 0.1 m and 0.2 m multifilament wire gauze packings, 0.0125 m double walled wire gauze partition rings and 0.025 m wire gauze saddle packings in columns operated countercurrently. The theory of gas absorption accompanied by fast pseudo mth order reaction was used to determine the effective interfacial area. The values of liquid side mass transfer coefficient for the multifilament wire gauze packings were obtained by absorbing lean carbon dioxide in a buffer solution of sodium carbonate and sodium bicarbonate. K_La values for the other packings were obtained by absorbing pure carbon dioxide in tap water. The values of a and k_La for multifilament wire gauze packings were found to be two to four times higher as compared to the conventional ring or saddle packings. Further, the superficial liquid velocity was found to have marginal effect on a. The double walled wire gauze partition rings offered a values which were 1.5–2.0 times higher than that offered by 0.016 m s.s. Pall rings at low values of superficial liquid velocity (<3 × 10^{?3 m/s}.     

Bubble size in a forced circulation loop reactor

BACKGROUND: The bubble size distribution in gas‐liquid reactors influences gas holdup, residence time distribution, and gas‐liquid interfacial area for mass transfer. This work reports on the effects of independently varied gas and liquid flow rates on steady‐state bubble size distributions in a new design of forced circulation loop reactor operated with an air–water system. The reactor consisted of a cylindrical vessel (～26 L nominal volume, gas‐free aspect ratio ≈ 6, downcomer‐to‐riser cross‐sectional area ratio of 0.493) with a concentric draft tube and an annular riser zone. Both gas and liquid were in forced flow through a sparger that had been designed for minimizing the bubble size. RESULTS: Photographically measured bubble size distributions in the riser zone could be approximated as normal distributions for the combinations of gas and liquid flow rates used. This contrasted with other kinds of size distributions (e.g. bimodal, Gaussian) that have been reported for other types of gas‐liquid reactors. Most of the bubbles were in the 3 to 5 mm diameter range. At any fixed low value of aeration rate (≤1.8 × 10^?4 m³s^?1), increase in the liquid flow rate caused earlier detachment of bubbles from the sparger holes to reduce the Sauter mean bubble size in the riser region. CONCLUSION: Unlike in conventional bubble columns where bimodal and Gaussian bubble size distributions have been reported, a normal bubble size distribution is attained in forced circulation loop reactors with an air–water system over the entire range of operation. Copyright © 2007 Society of Chemical Industry     

Mass Transfer Characteristics of Syngas Components in Slurry System at Industrial Conditions

The gas‐liquid mass transfer behavior of syngas components, H₂ and CO, has been studied in a three‐phase bubble column reactor at industrial conditions. The influences of the main operating conditions, such as temperature, pressure, superficial gas velocity and solid concentration, have been studied systematically. The volumetric liquid‐side mass transfer coefficient k_La is obtained by measuring the dissolution rate of H₂ and CO. The gas holdup and the bubble size distribution in the reactor are measured by an optical fiber technique, the specific gas‐liquid interfacial area aand the liquid‐side mass transfer coefficient k_L are calculated based on the experimental measurements. Empirical correlations are proposed to predict k_L and a values for H₂ and CO in liquid paraffin/solid particles slurry bubble column reactors.     

MEASUREMENT OF INTERFACIAL AREA AND MASS TRANSFER COEFFICIENTS BY CHEMICAL METHOD OF C02 ABSORPTION INTO AQUEOUS SOLUTIONS OF NaOH IN A MODEL COLUMN WITH EXPANDED METAL SHEET PACKING

The theory of gas absorption accompanied by fast pseudo-fast order reaction which considered dependences of diffusivity, kinetic constant and Henry's law constant on absolute temperature and ionic strength was used to obtain values of effective interfacial areas and mass transfer coefficients in gas and liquid phase.

Experimental measurement of carbon dioxide absorption from mixture with air was performed in a pilot-plant column with expanded metal sheet packing irrigated with sodium hydroxide solution.

Resulting liquid and gas-side mass transfer coefficients are compared with values obtained from physical Absorption measurement of carbon dioxide into water and with measurement of gas-side mass transfer coefficient for sulphur dioxide in the same column.

The differences between determined values are discussed.