Volumetric Gas-phase Mass Transfer Coefficients Research Articles

A green amino acid-based solvent blended with diethanolamine solution for CO2 capture using micro-contactor

The current research aims at developing an amino acid-based green technology containing a secondary alkanolamine (DEA) and L-arginine amino acid (ARG) for CO2 capture process from a gas stream in a T-type micro-contactor. To strengthen the understanding of the mass transfer of biodegradable green ARG in the micro-reactor, the mass transfer performance of CO2 absorption has been experimentally assessed under liquid flow rate (QL: 3.0–9.0 ml/min), gas flow rate (QG: 120.0–300.0 ml/min) at a constant temperature of 45 °C, and atmospheric pressure. The aqueous composition of the blended solution was DEA-ARG (35–0 wt%), DEA-ARG (31–4 wt%), DEA-ARG (27–8 wt%), and DEA-ARG (23–12 wt%). It was found that an increase in the solvent flow rate from 3.0 to 9.0 ml/min enhanced the CO2 absorption efficiency (θ), volumetric gas-phase mass transfer coefficient (KGaV), and volumetric molar flux (NGaV) by 2.5, 12.8, and 2.6%, respectively. However, an increase in the gas flow rate from 120.0 to 300.0 ml/min reduces the efficiency by 6% but improves the KGaV and NGaV by 88% and 225%, respectively. Additionally, the KGaV values followed a declining trend as the contribution of the DEA in the blended solution increased. Employing response surface methodology (RSM), the optimized values for CO2 absorption efficiency and KGaV were attained 92.93% and 69.40 kmol/m3 h kPa for QL of 9.0 ml/min, QG of 263.4 ml/min, and DEA-ARG concentration, CDEA-ARG of (23–12 wt%). Comparing the gas–liquid mass transfer characteristics of the aqueous DEA-ARG mixture with the traditional aqueous amine solutions, it was illustrated that the presence of L-arginine amino acid with high composition of 12 wt%, as a substitute organic promoter in aqueous DEA 35 wt%, can boost the performance of CO2 absorption process.

Intensification of HCl removal from flue gas using a rotor-stator reactor

The emission of HCl in flue gas causes serious environmental problems and its removal methods have attracted wide attention. This work investigated the intensification of HCl removal from flue gas in a rotor–stator reactor. The effects of high gravity factor, gas flow rate, water flow rate, temperature and inlet concentration of HCl on the removal efficiency of HCl, overall volumetric gas-phase mass-transfer coefficient (KGa) and height of a transfer unit in the removal of HCl by water in the rotor–stator reactor were investigated. Comparisons with conventional column indicated that the rotor–stator reactor had better mass-transfer performance and may have economic advantages in HCl removal. Comparison experiments showed that KGa and height of a transfer unit in the rotor–stator reactor were 10.9–45.2% higher and 41.5–55.7% lower, respectively, than those in a rotating packed bed, indicating that rotor–stator reactor has a superior capability for the removal of HCl in flue gas and other processes controlled by gas-side mass transfer. An artificial neural network model was established to predict the KGa of HCl removal from flue gas by water in the rotor–stator reactor. This work demonstrates that rotor–stator reactor is an effective process intensification technology for the removal of HCl from flue gas.

Mass transfer performance of rotating packed beds with blade packings in absorption of CO2 into MEA solution

This study investigates the mass transfer achieved using the rotating packed bed (RPB) with blade packings in the absorption of carbon dioxide (CO2) using monoethanolamine (MEA) solution. The overall volumetric gas-phase mass transfer coefficients (KGa) were evaluated using 1vol% CO2 and 1mol/L MEA solution in three RPBs with blade packings and the effects of rotational speed, gas flow rate, and liquid flow rate thereon were determined. The rotational speed positively influenced the KGa values for all RPBs. The obtained results revealed that the KGa values increased as the inner radius of the bed was increased, the outer radius of the bed was decreased, the liquid flow rate was increased or the gas flow rate was increased. The KGa values obtained using an MEA solution exceeded those obtained using an NaOH solution. The RPB with blade packings is a more effective gas–liquid contactor than one with structured packings in the absorption of CO2 using MEA solution.

Mass transfer performance of rotating packed beds with blade packings in carbon dioxide absorption into sodium hydroxide solution

This study investigated the mass transfer performance of the rotating packed bed (RPB) with blade packings in carbon dioxide (CO2) absorption by sodium hydroxide (NaOH) solution. The overall volumetric gas-phase mass transfer coefficients (KGa) were compared using 1vol% CO2 and 1mol/L NaOH solution for three RPBs with blade packings with the effects of rotational speed, gas flow rate, and liquid flow rate. As expected, the rotational speed positively affected the KGa values for all RPBs. Furthermore, the obtained results indicated that the KGa values increased as the inner radius of the bed was increased and the outer radius of the bed was decreased. Moreover, the KGa values increased with an increasing liquid flow rate and an increasing gas flow rate for all RPBs. According to the comparison with the RPB with structured packings, the RPB with blade packings had applicability in removing CO2 from the exhaust gas.

Process Intensification of Steel Slag Carbonation via a Rotating Packed Bed: Reaction Kinetics and Mass Transfer

Abstract The carbonation of alkaline wastes for CO 2 capture was mainly controlled by the CO 2 dissolution, i.e., mass-transfer controlled reaction, from the theoretical considerations. Several approaches to enhancing the CO 2 dissolution rate were proposed and investigated in the literature. For instance, it was proven that the rate of carbonation reaction for alkaline waste was effectively increase mass transfer rate if a rotating packed bed (RPB), so-called “high-gravity” or “HIGEE” process, was utilized. In this study, the experimental data were utilized to develop the carbonation model in an RPB for carbonation of various types of alkaline wastes such as basic oxygen furnace slag (BOFS) and cold-rolling mill wastewater (CRW). The effect of different operating parameters including operation modulus and rotating speed on CO 2 removal efficiency was evaluated. In addition, the overall volumetric gas-phase mass transfer coefficients (K G a) of BOFS/CRW carbonation in the RPB were calculated. Furthermore, according to the SEM observations, the alkaline wastes were found to be successfully carbonated with CO 2 in an RPB, where calcite (CaCO 3 ) was identified as the main product. It was thus concluded that accelerated carbonation of alkaline wastes using an RPB is an effective and efficient method for CO 2 capture due to its higher mass transfer rate and carbonation conversion.

Binary VOCs absorption in a rotating packed bed with blade packings

This investigation addressed the mass transfer of rotating packed beds with blade packings in removing methanol and 1-butanol from binary mixtures by absorption using water as the absorbent. The dependences of the overall volumetric gas-phase mass transfer coefficient (K(G)a) on the inlet methanol concentration, the inlet 1-butanol concentration, the rotational speed, the gas flow rate, and the liquid flow rate, were explored. The results demonstrated that the inlet methanol and 1-butanol concentrations had a negligible effect on the K(G)a values of methanol and 1-butanol. The K(G)a values of methanol and 1-butanol increased with the rotational speed, the gas flow rate, and the liquid flow rate. The dependence of K(G)a on the gas flow rate was higher than that on the liquid flow rate, revealing that the mass transfer in binary VOCs absorption may be controlled considerably by the mass transfer in gas phase.

Mass transfer performance of a rotating packed bed equipped with blade packings in removing methanol and 1-butanol from gaseous streams

The removal of methanol and 1-butanol from gaseous streams by absorption with water was investigated in the RPB equipped with blade packings. The overall volumetric gas-phase mass transfer coefficient (KGa) for methanol and 1-butanol absorption was observed to increase with the rotational speed, the gas flow rate, and the liquid flow rate. Also, the local volumetric gas-phase mass transfer coefficient (kGa) was estimated, and then the portion of the total resistance to mass transfer in gas phase was determined. The result indicated that more than 90% of the total resistance to mass transfer in methanol and 1-butanol absorption was found to be due to the gas phase. Comparison with the conventional packed tower demonstrated that mass transfer efficiency in the RPB equipped with blade packing was higher than that in the conventional packed tower. Consequently, the RPB equipped with blade packings would be an excellent absorber for the removal of alkanols from the exhausted gases.

Removal of ozone from air by absorption in a rotating packed bed

This work investigated the feasibility of ozone (O 3) absorption by H 2O 2 solution in a rotating packed bed (RPB). The overall volumetric gas-phase mass transfer coefficients ( K Ga) were determined as functions of pH of H 2O 2 solution, O 3 concentration, H 2O 2 concentration, RPB speed, gas flow rate, liquid flow rate, and RPB type. The K Ga values were highly dependent on the pH of H 2O 2 solution. Also, the K Ga values increased with O 3 concentration and H 2O 2 concentration. As expected, the RPB speed positively affected the K Ga values for all RPBs. Furthermore, the obtained results indicated that the K Ga values increased as the inner radius of the bed was increased and the outer radius of the bed was decreased. Moreover, the K Ga values increased with an increasing liquid flow rate and an increasing gas flow rate for all RPBs. The dependences of K Ga on the gas flow rate and the liquid flow rate indicated that the resistance to mass transfer in the gas-phase for O 3 absorption was higher than that in the liquid phase in the RPB.

Characteristics of cross-flow rotating packed beds

This work examined pressure drop and mass transfer of the cross-flow rotating packed bed (RPB) using absorption of carbon dioxide (CO 2) from gas. As to pressure drop, the gas flow rate was observed to be a more important factor than the rotor speed and the liquid flow rate due to less liquid holdup in the cross-flow RPB. The overall volumetric gas-phase mass transfer coefficients ( K G a) were determined as a function of the rotor speed, the gas flow rate and the liquid flow rate. The dependences of K G a on the gas flow rate and the liquid flow rate indicated that the resistance to mass transfer in the liquid phase for CO 2 absorption was higher than that in the gas phase in the cross-flow RPB. Moreover, the obtained results demonstrated that the K G a values of the cross-flow RPB were comparable to those of the countercurrent-flow RPB, suggesting a great potential of the cross-flow RPB applied to the removal of CO 2 from gaseous streams.

Absorption of VOCs in a Rotating Packed Bed

A Higee absorption process was developed to remove VOCs (volatile organic compounds) from air into an aqueous phase under a centrifugal field. The experimental results showed that the overall volumetric gas-phase mass-transfer coefficient (KGa) increased as a function of the gas Grashof number (GrG) to the power of 0.18. In analyzing kG and a individually, it was found that the enhancement of mass transfer by the centrifugal force can mainly be attributed to an increase in the effective gas−liquid interfacial area. The values of kG lie in a range similar to that for conventional packed beds.

SIMULTANEOUS ABSORPTION OF C02 AND H2S IN SULFINOL SOLUTIONS IN A SET OF PACKED ABSORBER-STRIPPER

Simultaneous absorption of CO2 and H2S in a Sulfinol solution have been studied in a set of small pilot scale packed absorber-stripper. Data were presented on the effects of varying liquid circulation rate, feed gas flow rate, feed gas composition and steam pressure at bottom of stripper, on the individual gas removal %, steam stripping efficiency and overall volumetric gas-phase mass transfer coefficient for absorption. A comparison with an earlier work on absorption into 20% hot potassium carbonate solution in the same apparatus show that the influence of operating variables on the performance of the absorber-stripper unit is qualitatively similar for both types of solvents except that the steam stripping efficiency of the Sulfinol system is much more superior than the 20% hot carbonate system under similar conditions. This shows that the hybrid nature of the Sulfinol solvent gives a much better regeneration efficiency than chemical solvents in simultaneous CO2 and H2S removal

Pressure drop and volumetric gas-phase mass transfer coefficient in a column packed with impulse packing.

Pressure drop and volumetric gas-phase mass transfer coefficient in a column packed with impulse packing.

Volumetric gas-phase mass transfer coefficient in baffled horizontal stirred vessels.

Volumetric gas-phase mass transfer coefficients based on the vessel volume, kGa'', were determined in baffled horizontal stirred vessels of four different diameters Dt from 0.159 to 0.493 m, equipped with turbine impellers, by absorption experiments on NH3-H2SO4 and H2S-NaOH systems, and by desorption experiments on HCN-NaCN system. The values of kGa'' are almost independent of the liquid holdup e in the range from 0.2 to 0.7. Also, the kGa'' values are not affected significantly by the number of impellers Ni or the ratio of vessel length to diameter L/Dt under the conditions of (L/Dt)/Ni<2 and l>0.67 D)t, where l is the distance between adjacent impellers. A dimensionless factor jD'', which is a modified jD factor, is defined and is used to correlate the data. The jD'' factor is found to be expressed in terms of dimensionless groups: the gas Reynolds number, the liquid Reynolds number based on impeller diameter and the Froude number Fr. Two relations between jD'' factor and these three dimensionless groups were obtained: one for Fr<0.2 and the other for Fr < 0.2, and the experimental results were represented by these equations with ±25% deviation.